#include "Stack.h"

void STInit(ST *ps)
{
    assert(ps);

    ps->a = NULL;
    ps->top = 0;
    ps->capacity = 0;
}

void STDestroy(ST *ps)
{
    assert(ps);

    free(ps->a);
    ps->a = NULL;
    ps->top = ps->capacity = 0;
}

// ջ
// 11:55
void STPush(ST *ps, STDataType x)
{
    assert(ps);

    // ˣ
    if (ps->top == ps->capacity)
    {
        int newcapacity = ps->capacity == 0 ? 4 : ps->capacity * 2;
        STDataType *tmp = (STDataType *)realloc(ps->a, newcapacity * sizeof(STDataType));
        if (tmp == NULL)
        {
            perror("realloc fail");
            return;
        }

        ps->a = tmp;
        ps->capacity = newcapacity;
    }

    ps->a[ps->top] = x;
    ps->top++;
}

void STPop(ST *ps)
{
    assert(ps);
    assert(!STEmpty(ps));

    ps->top--;
}

STDataType STTop(ST *ps)
{
    assert(ps);
    assert(!STEmpty(ps));

    return ps->a[ps->top - 1];
}

int STSize(ST *ps)
{
    assert(ps);

    return ps->top;
}

bool STEmpty(ST *ps)
{
    assert(ps);

    return ps->top == 0;
}